PITTSBURGH — The Pittsburgh Symphony Orchestra’s budget tripled in the last fiscal year, but $17 million in future funding is endangered, because it’s contingent on the orchestra balancing its budget. Symphony board Chairman Richard Simmons has pledged $12 million in funding if the symphony balances its budget for three consecutive years and $5 million from the Heinz Endowments requires back-to-back balanced budgets by the end of August 2015.